The invention relates generally to ferromagnetic films and composites, and particularly relates to flexible ferromagnetic composite substrates that may be applied to other substrates and articles.
Ferromagnetic films are generally films that include a magnetic material or a material that is capable of being magnetized. Such films are ubiquitous, finding application in a wide variety of commercial and educational uses. Flexible ferromagnetic films and composites are particularly suitable for a variety of uses including novelty items, white boards, advertisements, and hosts of applications for temporary signage.
Although such ferromagnetic films generally attach or stick well to magnetic and certain other metallic surfaces, they do not attach well to all surfaces such as those including glass, plastic, wood, paper etc. Materials and composites that include ferromagnetic material and an exposed adhesive material are known to be suitable for use in joining two articles together in a sandwich construction, but such composites are not suitable for use in applications where the composite includes a print receptive material that is exposed during use. For example neither the magnetic strips (20) disclosed in U.S. Pat. No. 5,366,070 nor the marker tape (10) disclosed in U.S. Pat. No. 4,442,152, are suitable for use in temporary signage, at least, because they are designed to be permanently sandwiched between other articles. U.S. Pat. No. 4,996,110 (the ""110 patent) discloses a white board including a layer of sheet-like magnet (5) adhered by an adhesive (3) to a polyester film (2). The sheet-like magnet (5) is disclosed to have magnetic properties as well as a light adhering property. The ""110 patent discloses that white boards of the ""110 patent are preferably used for application to steel surfaces wherein the light adhesive property inhibits movement of the white board during use. The ""110 patent also discloses that due to the light adhering property, the white board may be adhered to glass, decorative wood plate, and coated aluminum plates. Such white boards, however, do not exhibit sufficient adhesion to non-ferrous metallic surfaces to be suitable for a wide variety of uses. This is, in part, due to the fact that increasing the ratio by weight of ferromagnetic material to adhesive material in the sheet-like magnet generally decreases the adhesive strength of the adhesive material, while decreasing the ratio by weight of ferromagnetic material to adhesive material detracts from the magnetic strength of the sheet-like material.
There is a need, therefore, for a substrate that exhibits sufficient adhesive and ferromagnetic properties to be suitable for use in a wide variety of applications. Specifically, there is a need for a substrate that provides a strong adhesive force on its surface, yet also includes sufficient ferromagnetic material that the substrate may either produce a strong magnetic field or respond sufficiently to a strong magnetic field.
The invention provides a flexible composite substrate that includes a flexible carrier, a first adhesive and a second adhesive. The first adhesive is adhered to the flexible carrier and includes ferromagnetic material. The second adhesive is adhered to the first adhesive, and removably applies the flexible composite substrate to a receiving surface. The second adhesive has an adhesive strength that is greater than the adhesive strength of the first material. In various embodiments, composites of the invention may include carriers that are removable from the composite after the composite is applied to a receiving surface.